Synchronous drive



April 20, 1937. w. R. PERRY 2,077,768

SYNCHRONOUS DRIVE Filed Feb. 5, 1934 3 Sheets-Sheet l INVENTOR. Wi/liam1?. Perry,

J4 BY (f ATTORNEYS April 20, 1937. w. R. PERRY 2,077,768

SYNCHRONOUS DRIVE Filed Feb. 3, 1934 3 Sheets-Sheet 3 INVENTOR. WIN/am RPeary,

ATTORNEYS 25 step with the frequency generator.

Patented Apr. 20, 1937 PATENT OFFICE SYNGHRONOUS DRIVE William R. Perry,Columbus, Ind., assignor to Reeves Pulley Company, Columbus, 1nd,, acorporation of Indiana Application February 3, 1934, Serial No. 709,569

'7 Claims.

tary induction machines, which may sometimes be called hereinsynchronous motors, are electrically locked in step with said frequencygenerator; said machines operating, therefore, at the speed of thefrequency generator to drive power-receiving mechanisms.

It is an object of the prevent invention to overcome serious defectswhich have been inherent in organizations of this general typeheretofore known. Among such defects may be noted the tendency of theinduction machines to run away in case the operating circuits are closedat a time when the induction machines are out of step with thesupposedly dominating frequency' changer. It is an object of the presentinvention to provide means for preventing such a contingency.

In my prior Patent No. 1,757,734,.issued May 6, v 1930, I have providedmeans which tends to prevent the induction machines from getting out ofThe means disclosed in that patent will hold the induction machines instep with the frequency changer until such time as all of the machineshave cometo a stop; and thereafter all circuits will be 30 opened. Thatpatent discloses nothing to prevent some possible external force fromshifting the induction machines out of step with the frequency generatorafter the circuits have been opened. Furthermore, the device. of. thatpatent positively prevents the continued operation of the inductionmachines after the main power source or driving motor has been stopped.There are many instances, in industry, in which it is desirable tocontinue the operation of the subject machine'or machines after theparent or dominating machine has been stopped; and it is an object ofthe present invention to provide means whereby such continued operationof the subject machines is made possible.

It is a further object of the invention to provide means for positivelybringing the induction machines into step with the frequency generatorbefore operation of the frequency generator is initiated; therebypreventing any possibility of 50 the induction machines running away".

Further objects of the invention will appear as the descriptionproceeds.

To the accomplishment of the above and related objects, my invention maybe embodied in 5.3 the forms illustrated in the accompanying drawings,attention being called to the fact, however,

, that the drawings are illustrative only, and that change may be madein the specific constructions illustrated and described, so long as thescope of the appended claims is not violated.

Fig. 1 is a diagrammatic view of an industrial installation including aprime mover, variable speed means through whichsaid prime mover drives afrequency generator, and induction machines dominated by said frequencygenerator, for driving mechanisms auxiliary to a main mechanism drivenfrom the main driving motor;

Fig. 2 is a diagrammatic illustration of a similar organizationillustrating semi-automatic control means; and

Fig. 3 is a diagrammatic illustration of a similar organizationincluding fully automatic control means.

Referring more particularly to Fig. 1, it will be seen that I haveillustrated a. main driving motor l0 having spindle l operativelyconnected to drive the input shaft l2 of a variable speed transmissionl3 which, in the illustrated embodiment of my invention, is of the wellknown Reeves type. Said transmission l3 includes an output orvariable'speed shaft Hi, and a screw shaft l5, adapted to be operated bya hand-wheel l6, for

varying the speed differential between the shafts l2 and M.

The shaft l4 of the transmission I3 is, in the illustrated embodiment ofmy invention, operatively connected to drive the input shaft ll of asecond variable speed transmission l8 havin an output shaft IS. Thespeed differential between the shafts l1 and I9 is under the control ofa reversible pilot motor connected to drive a threaded shaft 2|; saidmotor being controlled by switch mechanism indicated at 22 and adaptedto be operated by a shaft 23. The particular switch mechanism forms nopart of my present invention, and consequently is not herein illustratedand described in detail. Suffice it to say that said mechanism is ofsuch character as to effect a non-hunting control of the speeddifferential between the shafts l1 and IS in response to oscillations ofthe shaft 23.

Said shaft 23 is under the control of a rod or lever 24 which is securedto the projecting end of said shaft.

'I'he shaft l4 carries a Worm 25 cooperating with a worm gear 26 mountedon a shaft 21 with which is associated a chain 28 driving a shaft 29upon which is mounted a calendering roll 30. A second roll 3| cooperateswith the roll 30 to compress a mass of rubber 32 into a sheet or ribbonTo the dance roll 35 is connected a cable 45 which passes upwardly overa sheave 46 and is connected to the outer end of the lever 24. A cable41, likewise connected to the outer end of the lever 24, passes over asheave 43 and supports a balance weight 43. Obviously, as the bight inthe ribbon 33 is shortened, the outer end of the lever 24 will beshifted to the right, as viewed in Fig. 1; and, as said bight islengthened, the outer end of said lever will be shifted to the left.

As the ribbon 33 issues from the vat 34, it is received upon a longconveyor 53 of the belt type running over rolls 5| and 52. The roll 52is mounted upon a shaft 53 which is driven, through a chain 54, from ashaft 55; said shaft 55 carrying a worm gear 56 meshing with a worm 51carried on the shaft 53 of a rotaryi duction machine 53. A second chain63, likewise driven from the shaft 55, drives the main shaft 6i of atread cutter illustrated diagrammatically at 62.

The variable shaft I3 of the transmission I3 is operatively connected todrive the shaft 63 of a frequency generator 64; and said frequencygenerator is electrically connected, in a manner hereinafter to bedescribed, to dominate the machines 44 and 53.

In practice, the conveyor 53 of this installation is some 400 feet long.It is obviously necessary to continue the operation of said conveyor andthe tread cutter 62 for a relatively long period after the last of aday's run of rubberhas passed between the rolls 33 and 3|. Obviously, itwould be uneconomical to continue to drive the heavy rolls 33 and 3|during a long period in which those rolls will be doing no useful work.It is, therefore, desirable to provide means whereby the machine 53, andperhaps the machine 44, may be continued in operation after the motor I3has been stopped.

Obviously, however, unless means can be provided whereby the machines 44and 53 may be positively brought back into step with the generator 64after such operation, such a scheme of operation would be highlyimpractical.

I have provided means whereby the above-mentioned economy may bepractically effected.

In-Fig'. 1, I have indicated a source of electrical energy in the formof a three-phase alternating current electrical circuit indicated by thewires 65, 66, and 61. Wires 63, 63, and 13 lead from said line wires,respectively, through a switch 1|, to the three terminals 12, 13, and14, respectively, of the main driving motor I3.

A switch 15, having three blades 16, 11, and 13, is adapted to connectthe wires 66, 66, and 61, through fuses 13, with terminals 33, 3i, and82, respectively.

A wire 33 connects the terminal 33 with one stator terminal 84 of thefrequency generator 64. A wire 35 connects the terminal 3| with anintermediate stator terminal 36 of said generator 64; and a wire 31connects the terminal 32, through a switch 83. with a wire 33. which isconnected to a wire 33 leading to the third terminal 3I of saidgenerator 64.

The stator terminals of.the machine 44 are connected in parallel withthe terminals 34, 36, and 3|. A wire 32 connects wire 33 with terminal33; a wire 34 connects wire 35 with terminal 35; and a wire 36 connectswire 33 with terminal 31 of said machine 44.

The stator terminals of the machine 53 may be likewise connected inparallel with the terminals 34, 36, and 3I. Thus, a wire 33 connects thewire 83 with terminal 33 of said machine 53. A wire I33 leads to acontact III which may be connected, through one blade I32 of a switchI33, with a terminal I34 which, in turn, is connected by wire I35 withterminal I36 of the machine 53. The wire 33 leads to contact I31 whichmay be connected,- through blade I33 of switch I33, with terminal I33which is connected by wire II3 with terminal III of the machine 53.

It will thus be seen that, when the switch 33 is closed, and when theblades I32 and I33 of switch I33 are respectively in contact withcontacts IM and I31, the stators of the three machines 64, 44, and 53will be energized through parallel circuits.

The frequency generator 64 includes slip ring contacts H2, H3, and H4. Awire II5 connects the contact I I2 with a wire 6 leading toone slip ringcontact II1 of the machine 53. A wire II3 connects the contact II3 witha wire II3 leading to a contact I23 which may be connected, throughblade I2I of switch I63, with terminal I22 which is connected, throughwire I23, with slip ring contact I24 of machine 53. A wire I25 connectsthe contact II4 with a wire I26 leading to a contact I21, which may beconnected, through blade I23 of switch I33, with terminal I23; and awire I33 connects said terminal I23 with the slip ring contact I3I ofmachine 53.

A wire I32 connects wire II6 with slipring contact I33 of machine 44. Awire I34 connects wire II3 with a slip ring contact I35 of machine 44;and a wire I36 connects wire I25 with slip ring contact I31 of machine44.

It will thus be seen that, when the switch I33 is in the positionillustrated, the slip ring contacts H2, H3, and H4 are connected,through parallel circuits, with the slip ring contacts Ill,

I24, and I3I, and the slip ring contacts I33, I35,

and I31.

A wire I33 leads fromwire 33 to a contact I33 adapted to be contacted bythe blade I33 of switch I33. A wire I43 leads from terminal 32 tocontact I adapted to be contacted by blade I32 of switch I33. When saidblades I62 and I63 are moved into contact with contacts I" and I33,terminals 3I and 32 will be connected with stator terminals III and I36,respectively, of the machine 53.

When the organization illustrated in Fig. 1 is to be put into operation,the switch 16 is closed, the switch 33 being in open pmition, and theswitch I 33 being in the position illustrated. Thereby, stator terminals34 and 36 of the frequency generator 64, stator terminals 33 and 35 ofthe machine 44, and stator terminals 33 and I36 of the machine 63 areconnected with the line wires 65 and 66, respectively. Simultaneously,slip ring contacts H2, H3, and H4 of the generator 64 are respectivelyconnected electrically with the slip ring contacts I", I24, and I3I ofthe machine 53, and with the slip ring contacts I33, I35, and I31 of themachine 44.

Itwillthusbeseenthatalloftheslipring contacts of both of the machines 44and 59 are connected with the slip ring contacts of the generator 64,and that the stator windings of the generator 64 and of the machines 44and 59 are energized withsingle phase current. I have discovered that,when those three machines are so connected and energized, the rotors ofthe machines 44 and 59 will be immediately jerked into step with therotor of the generator 64 (said generator being held stationary) withoutany tendency to run away from the generator.

This action is substantially instantaneous; so that, after the operatorhas closed the switch 15 (the switch I03 being in the illustratedposition) I he may immediately close the switch 88. When the switch 88is so closed, the stator terminals 9I of the machine 64, 91 of themachine 44, and III of the machine 59 are connected with the line wire61; whereby the organization comprising said three machines is placed incondition for the desired synchronous operation. Thereafter, theoperator closes the switch H to energize the motor I0; and the wholeinstallation will begin operation.

After a desired cycle of operation has been completed, so far asconcerns the rolls and EN blades I02 and, I08 contact the contacts I4!and I39, respectively. Thereby, the slip ring contacts H3 and H4 aredisconnected from the wires I23 and I30; and so from the slip ringcontacts I24 and I3I of the machine 59. At the same time, the rotorwindings of machine 59 are short-circuited by contact of the switch armsI28 and I2I with the contacts I28 and I2I'. It will be seen thatterminal H1 is connected to contacts I28 and I2I' by wire II6; terminalI24 is connected to arm I2I by wire I23; and terminal I3I is connectedto arm I28 by wire I30. The stator terminals 99, I06, and III of saidmachine 59 are still energized, however, through the wire 98 and thewires I38 and I40 through the switch blades I02 and I 08. Thus, thelock-in between the machine 59 and the generator 64 is broken, and themachine 59 continues to run as an induction motor.

The operator may now open the switch 88, thereby deenergizing the wire90, and so deenergizing the stator terminal 9I of the generator 64 andthe stator terminal 91 of the machine 44. The switch H is then opened,and the installation, with the exception of the machine 59 and theelements driven thereby, will coast to a stop.

The machine 59 will then continue to operate as an induction motor untilthe switch 15 is opened, or until the switch blades I02 and I08 aremoved out of contact with the contacts MI and I39.

In Fig. 2, I have illustrated an organization quite similar to theorganization illustrated in Fig. 1, but in which the control issemi-automatic in character; and in which no independent operation ofthe rotary induction machines as independent motors is contemplated. Forsimplicity, I have omitted from Fig. 2 any illustration of mechanismdriven by the various motors.

I have illustrated a main driving motor I having a shaft I5I which isconnected, by a chain to be operated by a hand-wheel I51 is illustrated,said control shaft being operable to vary the speed diiferential betweenthe shafts I 53 and I55.

A belt or chain I55 provides a driving connection between the shaft I55and the spindle I58 of a frequency generator I59.

I have illustrated two rotary induction machines I60 and I 6i suitablyelectrically connected with the generator I59 in a manner to bedescribed hereinafter.

A source of three phase alternating current is indicated by the linewires I62, I63, and I64. Said ine wires are adapted to be connected.through a switch I and fuses I66, with wires I61, I68, and I69,respectively. Said wires I61, I68, and I69 lead, respectively, toterminals I10, HI, and I12 which are adapted, at times, to be connected,respectively, to terminals I13, I14, and I15 through bridge pieces I16,I11, and I18 carried on a plunger I19 forming the core of a solenoidcoil I80. The terminals I13, I14, and I15 are connected, respectively,through wires I8I, I82, and I83, with the stator terminals I84, I85, andI86 of the main driving motor I50.

Obviously, when the bridge pieces I16, I11, and

I18 are moved into bridging relation with the terminals I10 and I13, Illand I14, and I12 and I15, respectively, the driving motor I50 will beenergized to drive the organization.

A wire I81 leads from the wire I69 to a terminal I88 which is adapted,at times, to be electrically connected with a terminal I89 through abridge piece I90 carried on a plunger I9I forming the core of a solenoidcoil I92. A wire I93 leads from the terminal I89 to one stator termi nalI94 of the frequency generator I59.

A wire I95 connects the wire I68 with a terminal I96 which, at times, isadapted to be electrically connected with a terminal I91 through abridge piece I98 carried on the plunger I9I. A wire I99 leads from saidterminal I91 to a second stator-terminal 200 of the generator I59.

A Wire 20I connects the wire I61 with a terminal 202 which is adapted,at times, to be electrically connected with a terminal 203 through abridge piece 204 carried upon a plunger 205 forming the core of asolenoid coil 206. A wire 291 leads from said terminal 203 to the thirdstator terminal 208 of the machine I59.

A wire 209 connects the wire I93 with one stator terminal 2I6 of themachine I6I; a wire 2II connects the wire I99 with a second statorterminal 2I2 of said machine; and a wire 2I3 connects the wire 201 withthe third stator terminal 2M of said machine I6I. the wire I93 with afirst stator terminal 2I6 of the machine I60; a wire 2I1 connects thewire I99 with a second stator terminal 2I8 of said machine; and a wire2I9 connects the wire 2I3 with the third stator terminal 220 of saidmachine I60.

It will thus be seen that the stators of the machines I59, I60, and I6Iare adapted to be energized through parallel three phase circuits.

The machine I59 is provided with slip ring contacts 2M. 222, and 223.The contact 22I is connected through Wires 224 and 225 to thecorresponding slip ring contact 225 of the machine I60; the contact 222is connected through Wires 221 and 226 with the corresponding contact229 of the machine I60; and the contact 223 is connected through wires230 and 23I with the corresponding contact 232 of said machine I66. Saidwires 224, 221, and 230 are continued to respective connections with theslip ring contacts 233,

A wire 2I5 connects til) 294, and 299 of the machine "I. Thus it will beseen that the slip ring contacts of the machine I99 areparallel-connected with the corresponding contacts of the machines I99and "I.

A wire 299 leads irom the wire I91 to a wire 231 which, in turn, isconnected with a terminal 299 adapted, at times, to be electricallyconnected with a terminal. 299. A bridge piece 249 is assoelated with apush button 2, and is normally held (by means not shown) out of bridgingrelation with the terminals 299 and 299. 242 leads from the terminal 299to a wire 249 which, in turn, is connected to one terminal 244 of thesolenoid coil I92. The opposite terminal 249 of said coil is connectedby a wire 249 with a wire 241 which leads to a terminal 249. Saidterminal 249 is normally electrically connected with a terminal 249through a bridge piece 299 provided with a stem 29I. A wire 292 connectsthe terminal 249 with the wire I99.

If the button 24I is depressed at a time when the switch I99 is closed,a circuit energizing the solenoid coil I92 will be established asfollows:- Line wire I92, switch I99, wire I91, wire 299, wire 291,terminal 299, bridge piece 249, terminal 299, wire 242, wire 249,terminal 244, coil I92, terminal 249, wire 249, wire 241, terminal 249,bridge piece 299, terminal 249, wire 292, wire I99, and switch I99 toline I94.

Such energization of the coil I92 elevates the plunger I9I to bring thebridge piece I99 into bridging relation with the terminals I99 and I99;to bring the bridge piece I99 into bridging relation with the terminalsI99 and I91; and to bring the bridge piece 299, likewise carried on saidplunger I9I, into bridging relation with associated terminals 294 .and299. Thereby, the generator I99 and the machines I99 and IN have theirstator windings energized with single phase current through circuits asiollows:Line wire I99, switch I99, wire I99, wire I99, terminal I99,bridge piece I99. terminal I91, wire I99, terminal 299, terminal I94,wire I99 (and, in parallel, through wires 2 and 2I1 to terminals 2 and2I9, and from terminals 2I9 and M9 through wires 299 and 2I9 to wireI99), terminal I99, bridge piece I99, terminal I99, wire I91, wire I99,and switch I99 to line wire I94.

Thereby, the rotors of the machines I99 and I9I are jerked into stepwith the rotor of the generator I99, without any tendency to "run away".

The above noted movement of the bridge piece 299 into bridging relationwith the terminals 294 and 299 establishes a holding circuit for thecoil I92 as followsz-Line wire I92, switch I99, wire I91, wire 299, wire299, terminal 299, bridge piece 299, terminal 294, wire 291, wire 249,terminal 244, coil I92, terminal 249, wire 249, wire 241, terminal 249,bridge piece 299, terminal 249, wire 292, wire I99, and switch I99 toline wire I94.

Since this holding circuit is independent of the terminals 299 and 299,the button 2 may be released immediately upon energization of the coilI92.

Simultaneously-with the establishment of the initial circuit energizingthe coil I92, there is established a safety circuit as i'ollowsz-Linewire I92, switch I99, wire I91, wire 299, wire 291, terminal 299, bridgepiece 249, terminal 299, wire 242, wire 299, terminal 299, normallyclosed bridge piece 299 on plunger I19, terminal 29I, wire 292, terminal299 oi solenoid coil 294, terminal 299, wire 241, terminal 249, bridgepiece 299, terminal 249, wire 292, wire I99, and switch I99 to line wireI94. Energization of the coil Awire' 294 is held through the bridgepiece 299 as followsz-Line wire I92, switch I99, wire I91, wire 299,wire 299. terminal 299, bridge piece 299. terminal 294, wire 291, wire242, wire 299, terminal 299, bri e piece 299, terminal 2". wire 292,terminal 9, coil 294, terminal 299, wire 241, terminal 249, bridge piece299, terminal 249, wire 292, wire I99, and switch I99 to line wire I94.

The core of the solenoid 294 comprises a plunger 299 carrying a piston291 provided with a restricted aperture 299, said piston working in afluid-filled cylinder 299. This construction delays the movement of theplunger 299. The upper end of the plunger 299 is aligned with the stem29I oi the bridge piece 299 so that, ii energization oi the coil 294 iscontinued beyond a predetermined period, said plunger will engage saidstern 29I to lift the'bridge piece 299 out of bridging relation with theterminals 249 and 249 to break the control circuits. It will be notedthat all control circuits heretofore described have included the bridgepiece 299; and. as the description proceeds, it will be seen that allintermediate control circuits hereinafter described will also includesaid bridge piece 299. Thus it will be seen that, unless the cycle ofcontrol operations is completed before the plunger 299 attains the upperlimit of its travel, the elements oi the control organization will bereturned to a condition of rest.

It is to be understood that the operations of the various elements ofthe control organization will take place substantially instantaneously.Immediately after initial depression of the button I, the rotors of themachines I99 and I9I will jerk in step with the rotor of the generatorI99.

Said button may be released immediately, and the operator will thenimmediately depress button 2II which carries bridge piece 219. Means(not .shown) are provided for normally holding the bridge piece 219 inthe position illustrated. Upon depression of the button 2', the bridgepiece 219 will be moved into bridging relation with the terminals 212and 219, thereby establishing a circuit for energizing the solenoid coil299, as follows:Line wire I92, switch I99, wire I91, wire 299, wire 299,terminal 299, bridge piece 299, terminal 294, wire 291, wire 242, wire219, terminal 219, bridge piece 249, terminal 211, wire 219, terminal212, bridge piece 219, terminal 219, wire 219, wire 299, terminal 29I,coil 299, terminal 292, wire 299, wire 249, wire 241, terminal 249,bridge piece 299, terminal 249, wire 292, wire I99, and switch I99 toline wire I94. Energization of the coil 299 elevates the plunger 299 tomove the bridge piece 294 into bridging relation with the terminals 292and 299; thereby completing three phase energization of the statorwindings of the machines I99, I99, and III. The organization includingthe three synchronized machines is now in condition for the desiredsynchronous operation.

When the plunger 299 is so elevated, a bridge piece 299 carried on saidplunger 299 is moved into bridging relation with a pair of terminals 299and 291. Thereby, a holding circuit for the coil 299, independent of theterminals 212 and 249, wire 252, wire I69, and switch I65 to line wireI64.

The button 2" may now be released.

It will be noted that the circuits energizing the coils I92 and 206 arestilPdependent upon the bridge piece 250; and that the coil 264 is stillenergized. It is necessary, therefore, for the operator immediately todepress button 289 carrying'bridge piece 290, whereby said bridge piece290 is moved into bridging relation with terminals 29'I and 292.Thereby, there is established a circuit energizing the coil I80, asfollows:'Line Wire I62, switch I65. wire I61, wire 236, wire 256,terminal 255, bridge piece 253, terminal 254, wire 251, wire 242, wire215, terminal 216, bridge piece 240, terminal 211, wire 218, wire 284,terminal 285, bridge piece 286, terminal 281, wire 288, wire 280, wire293, terminal 294, bridge piece 210, terminal 295, wire 296, terminal291, bridge piece 298 of stop button 299, terminal 300, wire 30I,terminal 292, bridge piece 290, terminal 29I, wire 302, wire 3I3,terminal 303 of coil I80, terminal 304, wire 305 overload relays 306,wire 301, wire 252, wire I68 and switch I65 to line wire I64.

Energization of 4 said coil I80 elevates the plunger I19, therebyclosing the energizing circuit for the motor I50 through the bridgepieces I16, I11, and I18. Such movement of the plunger I19 breaks theenergizing circuit for the coil 264 by moving the bridge piece 260 outof bridging relation withthe terminals 259 and 26I.

It will be seen that this energizing circuit for the coil I80 isindependent of the bridge piece 250.

Such movement of the plunger I19 further establishes a holding circuitfor the coil I80 independent of the bridge piece 290, as follows: Linewire I62, switch I65, wire I61, wire 236, wire 256, terminal 255, bridgepiece 253, terminal 254, wire 251, wire 242, wire 215, terminal 216,bridge piece 240, terminal 211, wire 218, wire 284, terminal 285, bridgepiece 286, terminal 281, wire 288, wire 280,-wire 293, terminal 294,bridge piece 210, terminal 295, wire 296, terminal 291, bridge piece298, terminal 300, wire 30I, wire 308, terminal 309, bridge piece 3I0,terminal 3, wire 3I2, wire 3I3, terminal 303, coil I80, terminal 304,wire 305, overload relays 306, wire 301, wire 252, wire I69, and switchI65 to line wire I64.

Immediately uponenergization of the coil I80, therefore, the button 289may be released; and the organization will continue in operation untilsuchtime as the last-traced circuit is deenergized. Such deenergizationof the holding circuit may be effected by depressing the button 299, orby the opening of one or more of the contacts of the overload relay 306.Thereby the circuit between the terminals 291 and 300 is broken. Whenthe circuit is so'brokemthe coil I80 is deenergized to break theoperating circuit for the motor I50. When the plunger 'I19' drops, thebridge piece 260 closes, between theterminals 259 and 26I, the circuitfor energizing the coil 264. The actiondelaying means associated withthe plunger 266 is so calibrated as to permit the machines I50,

I59, I60, and I6I to coast to a stop (the machines I59, I60 and I6Ibeing still locked in synchronism) before the plunger 266 will break thecircuits energizing the coils I92, 206, and 264,

tion of mechanism driven by the various electrical machines. a

A main driving motor 320 is connected to drive the input shaft 32I of avariable speed transmission 322, said transmission including a shaft 323for varying the speed differential between said input shaft and theoutput shaft 324 thereof. Said output shaft 324 is connected .to drive afrequency generator 325 having the usual slip rings 326, 321 and 328.Wires 329, 330 and 33I respectively, connect to said slip rings the sliprings 332, 333 and 334 of a rotary induction machine 335. Other wires336, 331 and 338 connect to the slip rings 326, 321 and 328,respectively,

wires 339, 340 and 34I connected to the slip rings 342, 343 and 344 of asecond rotary induction machine 345.

All of the machines 320, 325, 335 and: 345 are wound to be energizedthrough a polyphase fourwire system.

A source of electrical energy is indicated by the four line wires 346,341, 348 and 349. A fourblade switch 350 is adapted to connect said linewires, through fuses 35I, to wires 352, 353, 354 and 355, respectively.

A wire 356 leads from the wire 352 to a contact 351 which is adapted tobe electrically connected, by a bridge piece 358, with a contact 359which is connected, by a wire 360, with one terminal 36I of the motor320. The wire 353 is connected to a contact 362 which is adapted to beelectrically connected, by a bridge piece 363, with a contact 364 whichis connected, by a wire 365, to a second terminal 366 of the motor 320.The wire 354 is connected to a contact 361 which is adapted to beelectrically connected, by a bridge piece 368, with a contact 369 whichis connected, by a wire 310, a third terminal 31l of said motor 320. Thewire 355 is connected to a contact 312'which is adapted to beelectrically connected, by a bridge piece 313, with a contact 314 whichis connected, by a wire 315, to the fourth terminal 316 of the motor320.

All of said bridge pieces 358, 363, 368 and 313 are carried upon aplunger 311 which constitutes the core of the solenoid coil 318. Saidplunger 311 further carries two other bridge pieces 502 and 541.

A wire 319 leads from the wire 352 to a contact 380 which is adapted tobe connected, by a bridge piece 38I, with a contact 382. A wire 383leads from said contact 382 and is connected, by a wire 384, with a wire385 leading to a stator terminal 386 of the frequency generator 325. .Awire 381 connects said wire 384 with a stator terminal 388 of the rotaryinduction machine 335.

A second stator terminal 389 of the machine 325 is connected, by a wire390, with a wire 39I which leads through a wire 392, to a contact 393adapted to be electrically connected, by a bridge piece 394, with acontact 395 which is connected, by a wire 396, with the wire 353. Thecorresponding terminal 391 of the rotary induction machine 335 islsigewise connected, by a wire 398, with the wire The bridge pieces 38Iand 394 are carried on a plunger 520 which constitutes the core of asolenoid coil 5I9.

The wire 383 leads to a.v contact 399 which is adapted to be connected,by a bridge piece 400,

with a contact 40I which is connected, by a wire 402, to a statorterminal 403 of the machine 345. A second terminal 404 of said machineis con nected, by a wire 405, with a contact 406 which is adapted to beconnected, by a bridge piece 401,

with a contact 433 to which is connected the wire 332. A wire 433 leadsfrom the wire 354 to a contact 4lli which is adapted to be connected, bya bridge piece 4, with a contact 412 to which is connected a wire 3leading to a wire 4 which, in turn, leads to a third stator terminal 4|5 of the machine 335. The fourth stator terminal 3 of said machine 335is connected, by a wire 4l1, with a wire 4l3, which leads to a contact4i3.

Said contact 3 is adapted to be connected, by a bridge piece 423, with acontact 42! connected, by a wire 422, with the wire 355. A wire 423leads from the wire 4 to the third stator terminal 424 of the machine325; and the fourth stator terminal 425 of said machine 325 isconnected. by

a wire 425 with the wire 4l1.

The wire 4 connects the wire 4l3 not only with the terminal 5 and thewire 423, but also with a contact 421 which is adapted to be connected,.by a bridge piece 423, with a contact 423 to which is connected a wire433 leading-to the third stator terminal 431 of the machine 345. Thefourth stator terminal 432 of'said machine is connected by a wire 433with a contact 434 adapted to be connected, by a bridge piece 435,

with a contact 433 to which the wire 411 is confiected.

The bridge pieces 433, 431, 423, 4, 435 and 423 above-mentioned, are allcarried upon a 3 plunger 434 which constitutes the core of a solenoidcoil 453. Said plunger likewise carries further bridge pieces 435 and433.

A wire 431 leads from the wire 352 to a contact 433 which is adapted tobe connected, by a bridge piece 433, with a contact 443 which isconnected by a wire 553, with the terminal 433 of the machine 345. Theterminal 434 of said machine is connected byfa wire 4, to a contact 442which Q is adapted to be connected by a bridge piece 44:,

with a contact 444 which is connected, by a wire 445, with the wire 353.A wire 443 leads from the wire 354 to-a contact 441 adapted to beconnected, bya bridge piece 443, with a contact 443 which is connected,by a wire 453, with the ter- 45 minal 432 of the machine 345. Theterminal 43l of said machine is connected, by a wire 451, with a contact452 which is adapted to be connected, by

a bridge piece 453, with a contact 454 connected by wire 455 with thewire 355.

The bridge pieces 433, 443, 443 and 453 are all carried upon a plunger533 which constitutes the core of a solenoid coil 53L Said plungerlikewise carries bridge pieces 432, 533, 515 and 511.

When the illustrated mechanism is to be 55 started, the starting button455 is depressed to move the bridge piece 451 carried thereby intobridging relation with contacts 453 and 453. The other elements of theorganization being in the positions illustrated, and the switch 353being closed, such depression of button 455 will establish a circuit'asfollows:

Line wire 341, switch 353, wire 353, wire 433, contact 43l, bridge piece432, contact 453, wire 454, contact 453, bridge piece 451, contact 453,

wire 435, contact 433, wire 431, solenoid coil 453, wire 453, wire 413,wire 4", wire 412, contact 413, normally closed bridge piece 414,contact 413, wire .411, wire 413, contact 413, normally-closed bridgepiece 433, contact'432, wire 433, wire 352 and switch 353 to line wire345. The bridge piece 414 has a depending stem 415 for a purpose laterto b'edescribed; and the bridge piece 433 is carried by a button 43|which may be depressed to break any circuit flowing through the bridgeus Piece '9- The establishment of the above-traced circuit energizes thecoil 453 to lift the plunger 434, whereby bridge pieces 435, 423, 435,4| I, 423, 431 and 433 are moved into bridging relation with theirrespective pairs of contacts, and whereby bridge piece 433 is moved outoi bridging relation with its pair of contacts 553 and 553. Suchmovement of said plunger establishes circuits for energizing the statorsof the machines 325, 335

and 345 with single-phase current, as follows:

Line wire 343, switch 353, wire 354, wire 433, contact 4", bridge piece4, contact 2, wire 3, wire 4, wire 423, terminal 424 of frequencygenerator 325, terminal 425 of said machine, wire 425, wire 4l1, wire 3,contact 3, bridge piece 423, contact 42!, wire 422, wire 355 and switch353 to line wire 343. This circuit energizes the stator of the machine325. The stator of the machine 335 is similarly energized through thehot wire 4 leading to the terminal 415 thereof, the terminal "5 beingconnected to the abovementioned wire 4l1. The stator of the machine 345is similarly energized through the circuit leading from the hot wire 413through wire 4, contact 421, bridge piece 423, contact 423, wire 433,terminal 431, terminal 432, wire 433, contact 434, bridge piece 435,contact 435, wire 4l1 to wire 413, and so back to line wire 345.

The slip rings of the three machines 325, 335 and 345 being connectedtogether, this energization of the stator windings of said machines-with single-phase current will jerk the machines 335 and 345 into stepwith the machine 325, without any possibility of overrunning of saidmachines 335 and 345.

Depression of the button 453 not only establishes the above-tracedcircuit for energizing the coil 433, but also establishes a parallelcircuit leading from hot wire 455 through wire 431, solenoid coil 433,wire 433 to wire 41!, and so, along the previously traced circuit, toline wire 345. Energization of the coil 433 tends to lift the plunger433 which'constitutes the core of said coil 433, and which carries abridge piece 431 adapted to establish electrical contact between thecontact 433 and the contact 432. At its lower end, the plunger 433carries a piston 433 working in a fluid-filled dashpot 434. Obviously,the dashpot will delay the upward movement of the plunger 433, givingthe machines 335 and 345 an opportunity to jerk into step with themachine 325 before anything else happens.

When the bridge piece 435 moves into bridging relation with its contacts433 and 431, there is established a holding circuit for the coil 453, as

follows:

Line wire 341, switch 353, wire 353, wire 453, contact 4", bridge piece432, contact 453, wire 454, wire 435, contact 435, bridge piece 435,contact431, wire 433, wire 431, coil 433, wire 453, wire 413, wire "I,wire 412, contact 413, bridge piece 414, contact 413, wire 411, wire413, contact 413, bridge piece 433, contact 432, wire 433, wire 352 andswitch 353 to line wire 343. The button 453 may now be released withoutdeenergizing the coil 433.

Closure of the bridge piece 435 likewise establishes a holding circuitfor the coil 433. That circuit runs from the hot wire 433 of the abovecircuit through wire 431, contact 453, wire 455, wire 431, coil 433,wire 433 to wire 4", and so to line wire 345.

When, after the above-mentioned delay, the

the contacts 455 and 492, there is established a circuit for energizingthe coil 505, as follows:

From the hot contact 455 through bridge piece 49!, contact 492, wire499, wire 500, contact 50!, bridge piece 502, contact 503, wire 504,coil 505 and wire 505 to wire 489 and wire "I, and so to the line wire345. The core 501 of said coil 505 carries at its lower end a piston 508working in a fluid filled dashpot 509 for delaying the action of saidcore. At its upper end, said core 501 carries an abutment l0 from whichextends upwardly a stem 5|! surrounded by a spring 5l2 bearing on theabutment 5l0 and supporting a bridge piece 5l3. Said stem-5H carries atits upper end an abutment 5l4 restraining the bridge piece 5l3 againstupward movement relative to said stem; but it will be clear that thestem 5 may move upwardly with relation to the bridge piece 5l3.

Said bridge piece will be moved, after a suitable delay, into bridgingrelation with contacts 5l5 and 515 for a purpose later to be described.

Closure of the bridge piece 491' likewise energizes a circuit, parallelto' that for energizing the coil 5l9, and which runs from the hotcontact 455 through bridge piece 49l, contact 492, wire 499, wire 5I1,contact 5l5, wire 518, coil 5l9 and wire 410 to wire 41!, and so to linewire 345. Energization of the coil 5I9 lifts the plunger 520 to move thebridge pieces 38l and 394 into bridge relation with their respectivepairs of contacts.

Thereby, the energization of the stator windings of the machines 325,335 and 345 with poly-phase current is completed through wiringpreviously described.

Still a third parallel circuit is energized by closure of said bridgepiece 49l, said circuit running from the hot contact 455 through bridgepiece 49 l contact 492, wire 499, wire 500, contact 50], bridge piece502, contact 503, wire 504, wire 52l, coil 522 and wire 523 to contact413, and so to line wire 345. A plunger 524 constitutes the core of thecoil 522 and carries at its lower end a piston 525 working in afluid-filled dashpot 525. The upper end of said plunger 524 is alignedwith the stem 415 of the bridge piece 414 so that, if, after he hasdepressed, the button 455, the operator does nothing more, the plunger524 will, after a delay of several seconds, engage said stem 415 to liftthe bridge piece 414. Since all of the above-described control circuitsrun through the bridge piece 414, the lifting of said bridge piece 414will, of course,break all circuits and return all of the parts to thepositions in which they are illustrated.

The coils 505 and 522, with their associated parts, are so arranged andproportioned that the bridge piece 5l3 will move into bridging relationwith its contacts 5l5 and 5" before the plunger 524 lifts the bridgepiece 414 out of bridging relation with its contacts 413 and 415. If,before said bridge piece 414 is lifted, the operator depresses thebutton 521 which carries a bridge piece 528, to move said bridge piece528 into bridge relation with its contacts 529 and 530, there will beestablished a circuit as follows:

From the hot contact 5|5 through bridge piece m, contact 5l5, wire,.53l,contact 529, bridge piece 528,"contact'530, wire 532, contact 533, wire534, solenoid coil 318, wire 535,. overload relay 535, wire 531,overload relay 538, wire 538, contact 540, normally-closed bridge piece5 of stop button 542, contact 543, wire 544, and wire 412 to contact413, and so to line wire 348.

Energization of the coil 318 through the abovetraced circuit will liftthe plunger 311 with its bridge pieces 358, 353, 358 and 313 toestablish an energizing poly-phase circuit for the main motor 320through wiring previously described. At the same time, the bridge piece502 will be moved out of bridging relation with the contacts 50! and 503to break the above-traced circuits through which the coils 505 and 522are energized.

The plungers 501 and 524 now begin to drop; but their downward movementis delayed by the action of the dashpots 509 and 525. The spring 5l2having been somewhat compressed, the bridge piece 5l3 will be maintainedin bridging relation with the contacts 5l5 and H5 for at least a shortperiod. Within that period, the plunger 311 will have time to move itsbridge piece 541 into bridging relation with its contacts 533 and 545 toestablish a holding circuit for 545, contact 545, bridge piece 541,'contact 533,

wire 534, coil 318, wire 535, overload relay 535, wire 531, overloadrelay 538, wire 539, contact 540, bridge piece 54!, contact 543 and wire544 to wire 412, and so to the line wire 345. Since this circuit isindependent of both the bridge piece 5l3 and the bridge piece 528, thebutton 521 may now be released.

' It will be seen that the coils 458, 5l9, 488 and 318 are allenergized, while the coils 505 and 522 are deenerglzed. The motor 320,the frequency generator 325 and the rotary induction machines 335 and345 are all properly energized, and the system is operating in acondition of equilibrium.

If, now, it is desired to stop theorganization, the operator presses thebutton 542, thereby moving the bridge piece 5 out of bridging relationwith the contacts 540 and 543, and breaking the holding circuit for thecoil 318. The plunger 311 instantly drops, deenergizing the motor 320.Of course, the motor 320 does not stop instantaneously but, togetherwith the machines 325, 335 and 345, will coast to a stop. The breakingof the circuit through the bridge piece 5 does not affect theenergization of the coils 458, 5l9 and 488; so that the machines 335 and345 remain locked in step with the machine325.

As the plunger 311 drops, the bridge piece 502 is moved into bridgingrelation with the contacts 50! and 503 to'establish circuits previouslydescribed through the cells 505 and522. If, by any chance, the operatorshould change his mind within a few seconds after having pressed thebutton 542, he may restart the system by pressing the button 521. If,however, he does not press the button 521, the plunger 524 will, after adelay of a few seconds within which time the machines 325, 335 and 345will coast to a stop, engage the stem 415 to lift the bridge piece 414out of engagement with the contacts 413 and 415 'to break the circuitsenergizing the coils 458, M9 and 488. The moment those circuits arebroken. the plungers 484 and 520' will drop to break the circuitsenergizing the windings of the machines 325, 335 and 345, and the systemwill be at rest in a condition of equilibrium.

It is to be noted that. in view of the delay in breaking the lockingcircuits, the machines 325, 335 and 345 will come to rest in step.

It is also to be noted that the organization may be stopped, as above,either by depressing the button 542, or thr ough the action of eitheroverload relay 555 or 555.

If it should be desired to stop the operation of the system temporarilyin such a manner as to avoid the necessity of waiting through the timedelay provided by the above-described system, the operator will pressthe button 545 of the switch 549 before pressing the button 542.Movement of the switch 549 into bridging relation with the contacts 555and 55l provides a shunt 'circuit around the bridge piece 414 forcarrying the various circuits energizing the coils 455, 5l5 and 455. Itwill be remembered that the energizing circuits for all of these coilsflow through the wire 4H and thence through the wire 412 and contact 413to and across the bridge piece 414 to the contact 415, wire 411 and wire415 With the switch 545 closed, these circuits may flow through the wire"I, wire 544, wire 552, contact 555, switch 549 and contact 55! to thewire 415, and so to the line wire 345.

'Thus, with the switch 549 closed, opening of the switch 542 will breakthe holding circuit for the coil 515, to stop the motor 525. As abovedescribed, dropping of the plunger 311 energizes the coils 555 and 522;but operation of the plunger 524 to lift the bridge piece 414 will notdeenergize the coils 455, 455 and H9, since energizing circuits forthose coils may now flow through the switch 549. The motor 525 may nowbe started immediately, a1ter any desired period of deenergization,simply by depressing the button 521: and without having to wait foroperation of the plungers 455 and 551.

Of course, even with the switch 545 closed,

depression 01' the button 45l will immediately deenergize all of thecontrolling coils, whereby the system will coast to rest without anylock-up control, and without any assurance that the ma- 40 chines 555and 545 will remain in step with the machine 525.

If it is desired to operate the machine 545 as a motor, entirelyindependently of machines 525,

as and as, the operator will depress the button 555 to move the bridgepiece 554 carried thereby bridging relation with the contacts 555 andAssuming the plunger 454 to be in the position illustrated, depressionof the button 555 energizes a circuit as follows:

Line wire 541, switch 555, wire 555, wire 455, wire 551, contact 555,bridge piece 455, contact 555, wire 55,5, coil 551, wire 552, contact555, bridge piece 554, contact 555, wire 554, wire 555,

wire555, contact 545, bridge piece 541, contact 545, wire 544, wire 412,contact 415, bridge piece 414, contact 415, wire 411, wire 415, contact415, bridge piece 455, contact 452, wire 455, wire 552 and switch 555 toline wire 545. The energization of coil 55l lifts the plunger 555 whichconstitutes the core oi said coil. Said plunger'carries bridge pieces455, 445, 445 and 455 which, upon such upward movement of the plunger,close a circuit for supplying four-wire polyphase current to the statorwindings oi' the machine 545. The plunger 555 likewise carries bridgepieces 515 and 511 which, upon upward movement oi the plunger 555,establish electrical contact between wires 515 and 515, respecmtivelyconnected to slip rings 542 and 545, and wire 555 connected to slip ring544. Obviously, so long as the plunger 555 isheld in its upper position,the machine 545 will run as a motor.

The plunger 555 likewise carries abridge piece 7 555 which, upon upwardmovement 01' said plunger, establishes electrical connection between thecontacts 555 and 515 to provide a holding. circuit for the coil 55lindependent of the button 555, as follows:

Line wire 541, switch 550, wire 355, wire 455. wire 551, contact 555,bridge piece 455, contact 559, wire 555, coil 55l, wire 551, contact555, bridge piece 559, contact 515, wire 51 i, wire 555, wire 559,contact 545, bridge piece 5, contact 543, wire 544, wire 412, contact413, bridge piece 414, contact 415, wire 411, wire 415, contact 419,bridge piece 4511, contact 452, wire 455, wire 552 and switch 555 toline wire 545.

The last-traced circuit will hold the plunger 555 in its upper positionuntil the button 542 or the button I is depressed, to break the same.

It will be noted that, when the plunger 555 is in its upper position,the control system is inoperative to lock the machines 525, 355 and 545together, since the initial control circuit which is the first one to beclosed by depression of the starting button 455, must flow through thebridge piece 452, which, when the plunger 555 is in its upper position,is out of contact with its contacts 45l and 455.

Similarly, when the machines 525, 555 and 545 are locked together, it isimpossible to energize the coil 55l, since the initial energizingcircuit for said coil must flow through the bridge piece 455 which, whenthe said machines are locked together, is out of contact with itscontacts 555 and 555.

To make assurance doubly sure, I prefer to provide a mechanicalinterlock between the plungers 454 and 555 whereby, when one of saidplungers is elevated, the other is mechanically held in its lowermostposition. Such interlock comprises .a lever, indicated generally at 512and pivoted intermediate its ends at 515. One arm 514 of said'lever isdisposed in the path of the plunger 454, and the other arm 515 isdisposed in the path of the plunger 555.

It may be appropriate to note here the fact that, ii the machine 525 isdriven mechanically in the direction 01 the rotating magnetic field, thelock-in torque between that machine and the machines 555 and 545 dropsofl' rapidly above of synchronous speed, and becomes zero at synchronousspeed; whereas, it the machine 525 is driven in the direction oppositeto the direction of field rotation the lock-in torque increases with anincrease of speed, but over-all eillciency is lower as a result of theproduction in the machines of a braking torque. The present inventionis, of course, entirely independent of the direction of rotation of themachines 525, 555 and 545.

I claim as my invention:

1. In combination, a source of polyphase electric current, a frequencygenerator, means for driving said generator, a synchronous rotaryinduction machine, means electrically connecting the secondary windingsof said generator with the secondary windings of said induction machine,at least three wires connecting the primary windings oi said generatorwith said source,

a switch controlling two of said wires, an electromagnet adapted, uponenergization, to move said switch to closed position, a second switchcontrolling at least one other of said wires, a second electromagnetadapted, upon energization, to move said second switch to closedposition, means connecting the primary windings of said inductionmachine with said wires at points separated from said source by saidswitches. a circuit for energizing said first electromagnet, a thirdswitch in said last-named circuit, a circuit for energizing said secondelectromagnet, and a fourth switch in said last-mentioned circuit, saidfourth switch being normally open and being controlled by a thirdelectromagnet energizable to move the same to closed position only uponclosure of said third switch by energization of said firstelectromagnet.

2. In combination, a source of polyphase electric current, a frequencygenerator, means for driving said generator, a synchronous rotaryinduction machine, means electrically connecting the secondary windingsof said generator with the secondary, windings of said inductionmachine, three wires connecting the primary windings of said generatorwith said source, a first electromagnet, a first switch dominated bysaid first electromagnet and controlling two of said wires and adaptedto be moved to closed position by energization of said firstelectromagnet, an energizing circuit for said first electromagnet, asecond electromagnet, a second switch dominated by said secondelectromagnet and controlling the third wire and adapted to be moved toclosed position by energization of said second electromag net, anenergizing circuit for said second electromagnet, means connecting theprimary windings of said induction machine with said three Wires atpoints separated from said source by said switches, and a third switchconnected in the energizing circuit for said second electromagnet anddominated by said first electromagnet, said third switch being moved toclosed position by energization of said first electromagnet.

3. In combination, a source of polyphase electric current, a frequencygenerator, means for driving said generator, a synchronous rotaryinduction machine, means electrically connecting the secondary windingsof said generator with the secondary windings of said induction machine,three wires connecting the primary windings of said generatorwith saidsource, a first electromagnet, a first switch dominated by said firstelectromagnet and controlling two of said wires and adapted to be movedto closed position by energization of said first electromagnet, anenergizing circuit for said first electromagnet, a second electromagnet,a second switch dominated by said second electromagnet and controllingthe third wire and adapted to be moved to closed position byenergization of said second electromagnet, an energizing circuit forsaid second electromagnet, means connecting the primary windings of saidinduction machine with said three wires at points separated from saidsource by said switches, a third switch connected in the energizingcircuit for said second electromagnet and dominated by said firstelectromagnet, said third switch being moved to closed position byenergization of said first electromagnet, athird electromagnet, anenergizing circuit for said third electromagnet and including said thirdswitch, and a fourth switch normally closed and connected in all of saidenergizing circuits, said third electromagnet being operable, upon theexpiration of a predetermined length of time after energization thereof,to open said fourth switch.

4. In combination, a source of polyphase electric current, a frequencygenerator, a synchronous rotary induction machine, means electricallyconnecting the secondary windings of said generator with the secondarywindings of said induction machine, three wires connecting the primarywindings of said generator'with said source, a

first electromagnet, a first switch dominated by said firstelectromagnet and controlling two of said wires and adapted to be movedto closed position by energization of said first electromagnet, anenergizing circuit for said first electromagnet, a second electromagnet,a second switch dominated by said second electromagnet and controllingthe third wire and adapted to be moved to closed position byenergization of said second electromagnet, an energizing circuit forsaid second electromagnet, means connecting the primary windings of saidinduction machine with said three wires at points separated from saidsource by said switches, a third switch connected in the energizingcircuit for said second electromagnet and dominated by said firstelectromagnet, said third switch being moved to closed position byenergization of said first electromagnet, a third electromagnet, anenergizing circuit for said third electromagnet and including said thirdswitch, a fourth switch normally closed and connected in ail of saidenergizing circuits, said third electromagnet being operable, upon theexpiration. of a predetermined length of time after energizationthereof, to open said fourth switch, an electric motor for driving saidgenerator, a circuit for en ergizing said motor, a fifth switch in saidmotor circuit, a fourth electromagnet dominating said fifth switch andadapted, upon energization, to close said fifth switch, and a normallyclosed sixth switch connected in the energizing circuit for said thirdelectromagnet and dominated by said fourth electromagnet and adapted tobe moved to open position upon energization of said fourthelectromagnet.

5. in combination, a source of polyphase electric current, a frequencygenerator, means for driving said generator, a synchronous rotaryinduction machine, means electrically connecting the secondary windingsof said generator with the secondary windings of said induction machine,three wires connecting the primary windings of said generator with saidsource, a first electromagnet, a first switch dominated by said firstelectromagnet and controlling two of said wires and adapted to be movedto closed position by energization of said first electromagnet, anenergizing circuit for said first electromagnet, a second electromagnet,a second switch dominated by said second electromagnet and controllingthe third wire and adapted to be moved to closed position byenergization of said second electromagnet, an energizing circuit forsaid second electromagnet, means connecting the primary windings of saidinduction machine with said three wires at points separated fromsaidsource by said switches, a third switch connected in the enerfourthswitch.

6. In combination, a source of electric current, an electric motor, afrequency generator driven by said motor, and a synchronous rotaryinduction machine having its secondary windings electrically connectedto the secondary windings of said generator, means operable, at times,to shortcircuit said windings of said induction machine, a circuit forsupplying current from said source to said motor, a first switchmechanism dominating said motor circuit, a first electrically actuatedmeans operable, upon energization, to move said first switch mechanismto circuit-closing position, parallel circuits for supplying currentfrom said source to the primary windings of said generator and of saidinduction machine, a second switch mechanism dominating said parallelcircuits, a second electrically actuated means operable, uponenergizationyto move said second switch mechanism to circuit-closingposition, a circuit for supplying current from said source to theprimary windings of said induction machine only, a third switchmechanism dominating said circuit, a

' third electrically actuated means operable, upon energization, to movesaid third switch to circuitclosing position, and means preventingenergization of said first electrically actuated means and preventingnergization of said second electrically actuated means when said thirdelectrically actuated means is energized.

'7. In combination, a source of electric current,

an electric motor, a frequency generator driven by said motor, and asynchronous rotary induction machine having its secondary windingselectrically connected to the secondary windings of said generator,means operable, at times, to shortcircuit said windings of saidinduction machine, a circuit for supplying current from said source 30to said motor, a first switch mechanism dominating said motor circuit, afirst electrically actuated means operable, upon energization, to movesaid first switch mechanism to circuit-closing position, parallelcircuits for supplying current from said source to the primary windingsoi! said lanerator and of said induction machine, a second switchmechanism dominating said parallel circuits, a second electricallyactuated means operable, upon energization, to move said second switchmechanism to circuit-closing position. a circuit for supplying currentfrom said source to the primary windings of said induction machine only,a third switch mechanism dominating said circuit, a third electricallyactuated means operable, upon energization, to move said third switch tocircuit-closing position, a circuit for energizing said firstelectrically actuated means, said circuit including a switch moved toopen position by energization of said third electrically actuated means,and including also a switch moved to closed position by energization ofsaid second electrically actuated means, a circuit for energizing saidsecond electrically actuated means, and including a switch moved to openposition by energization of said third electrically actuated means, anda circuit for energizing said third electrically actuated means andincluding a switch moved to open position by energization of said secondelectrically actuated means.

WILLIAM R. PERRY.

